What size front tires are or were on the car? I'm thinking that 185/60 or wider tires will cause rubbing or actual cracking of the inner wheel well area which if severe enough will crack the out side of the fender. It's happened to two of my S2s. You can check for tire to fender contact by turning the the front wheel to full lock and have somebody press down on the corner of the body and check for contact. The PO of my S2 was aware of the issue and cut out the inner fender lip where the tire was rubbing. Unfortunately running Toyo R888 185/6013 tires there is still some rubbing and the drivers side front fender now has a small crack and a big chip.
I've cracked the lip of the front wheel arch, directly above the centre-line of the wheel and tire, a couple of times. My original wheel-well closing plates are present. In my case it takes just a sharp bump, like the bump between the road and my driveway, with the wheels turned, and the top of the tire can contact the lip. I try to take this kind of situation slowly.
The original steel wheels on an S2 were 13x4-1/2 inches with an offset of 1-9/16 inch. The original tires were 155x13 and had a tread width of about 4 inches. I still have one, a Dunlop SP. There was no number for the profile but I believe it was 82 on tires of this period. A 155/82x13 tire has a height of 5.0 inches and a rolling diameter of 23.0 inches. I'm running 165/70x13 Michelins on the front on 5-1/2 inch rims with an offset of 1-5/8 inch. These tires have a tread width of about 5 inches, are 4-1/2 inches high, and have a rolling diameter of just over 22 inches. The wheels alone have the effect of pushing the outside of the tire 9/16 of an inch further out than the originals. Add half an inch for the greater tread width, and it seems to me that the outside of my tread is roughly an inch further out than the originals would have been, though the gap between the tread and the wheel arch should be a 1/2 inch greater than original.
Have my front springs settled half an inch over the years? Quite likely. That, and the increased width of my wheel/tire combination are likely the villains when it comes to my tires nibbling the lip of the wheel arch.
These tires rub slightly on the inside of the wheel-wells at full lock, more noticeably in reverse than going slowly forwards, and more noticeably with a passenger than with me alone. I think the villain here is simply the wider tires.
